The present invention relates to an automatic document feeder for an image forming apparatus such as copying apparatus. More particularly, the invention relates to an automatic document feeder for feeding a plurality of stacked documents one by one on to an optical exposure portion of the image forming apparatus.
Japanese Patent Laying Open Numbers. (KOKAI). 58-80667 discloses a conventional automatic document feeder for feeding a plurality of stacked documents one by one on to an optical exposure portion of a copying apparatus, in which a plurality of stacked documents are fed from the document tray one by one in order from the lowermost one thereof. Japanese Patent Laying Open Numbers (KOKAI). 61-166438, and 61-172165 disclose automatic document feeders, respectively, which are similar to that in the first reference.
Each of the above-mentioned conventional document feeders can feed not only single-sided image bearing documents, but also two-sided image bearing documents. However, in these conventional document feeders, since the documents are fed from the document tray in order from the lowermost one thereof, as mentioned above, they suffer from a disadvantage in that after being subjected to an optical exposure process, the documents having successive pages will be inconveniently stacked on the discharge tray in the state that the order of pages of the documents is opposite to that on the document tray.
On the other hand, in these conventional document feeders, the documents having successive pages are stacked on the document tray in the state that the image bearing surfaces of the documents are oriented upward, and that the uppermost document has a first page, while the lowermost document has a last page. In this case, when the image bearing pages of an odd number of single-sided image bearing documents are to be copied on opposite sides of transfer papers for producing two-sided copy papers, the conventional document feeders suffer from a disadvantage in that a blank page would be formed on the back side of a first page copied. In order to eliminate such a disadvantage, it is necessary to count the number of single-sided image bearing documents before a copying process is started.
Further, the document feeder of the above-mentioned type requires a relatively large and complicated document conveying path, particularly in a reversing circulation path.